The inventive concepts described herein relate to digital optical phase conjugation capable of making a scattered wave go back to an original wave source, based on a time-reversal characteristic of a wave.
The term “phase conjugation” is used to describe a phenomenon where after measuring of a scattered wave, the scattered wave is gone back to an original wave source according to a time-reversal characteristic of a wave when the scattered wave is returned with its phase inverted. In particular, the phase conjugation is mostly used for application techniques of fields including the following: sounds, ultrasonic waves, microwaves, or radio waves easy to measure a phase. However, since it is difficult to measure a phase with respect to a short wavelength, the practical use of the phase conjugation is not much in a visible light range.
A holographic crystal is mainly used for the phase conjugation in the visible light range. The holographic crystal generates phase conjugated light by recording a desired wavefront at a crystal together with reference light and changing the direction of the reference light. Problems caused when the crystal is practically used includes the following: restriction on a wavelength used to record information at the crystal, long time taken upon recording of light and separate time required upon recoding another wavefront at the crystal.
Thus, there is required a technique capable of generating phase conjugated light regardless of the length of wavelength and making it possible to produce phase conjugation faster.